We investigate the properties of latex particle templates required to optimize the development of ordered liquid bridge networks in evaporative lithography. These networks are key precursors in the assembly of solutions of conducting nanoparticles into large, optically transparent, and conducting microwire networks on substrates (Vakarelski, I. U.; Chan, D. Y. C.; Nonoguchi, T.; Shinto, H.; Higashitani, K. Phys. Rev. Lett., 2009, 102, 058303). An appropriate combination of heat treatment and oxygen plasma etching of a close-packed latex particle monolayer is shown to create open-spaced particle templates which facilitates the formation of ordered fully connected liquid bridge networks that are critical to the formation of ordered microwire networks. Similar results can also be achieved if non-close-packed latex particle templates with square or honeycomb geometries are used. The present results have important implications for the development of the particulate templates to control the morphology of functional microwire networks by evaporative lithography.

Antisolvent precipitation aided by polymeric additives has increasingly been explored as a method to produce micron-sized/submicron particles of active pharmaceutical ingredients with low aqueous solubilityso as to enhance their dissolution rate and absorption efficiency. This work is aimed toward understanding the role of these additives in mediating crystal nucleation and the growth process. Nucleation kinetics of naproxen, a poorly water-soluble drug, from an ethanol–water solvent mixture at various solute concentrations and in the presence of additives such as polyvinylpyrolidone (PVP) and hydroxypropyl methyl cellulose (HPMC) was investigated. At a given supersaturation, the crystal nucleation rate was calculated from probability distribution of the induction times measured in stirred, small-volume batch solutions. The analysis revealed that PVP additive significantly promotes the nucleation kinetics in the entire range of supersaturation examined, whereas the effect of HPMC on the nucleation kinetics is supersaturation-dependent. Furthermore, the nucleation rates determined as a function of supersaturation followed the trend predicted using the classical nucleation theory (CNT) and indicated the occurrence of heterogeneous nucleation. Thermodynamic and kinetic parameters derived from the CNT equation, together with the crystal habit and size data, were used to elucidate the mechanisms underpinning the effect of polymeric additives on nucleation kinetics.

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